Thomas R. Loree

Spectrochemical Analysis of Liquids Using the Laser Spark

A laser-generated spark was used to analyze liquids spectroscopically for elemental constituents The spark was produced directly in liquids by a focused laser pulse of 15 ns duration and an energy of about 45 mJ/pulse The size, temperature, and electron density of the spark are reported Emissions from once-ionized and neutral atoms and simple molecules were observed Limits of detection for Li, Na, K, Rb, Cs, Be, Mg, Ca, B, and Al in aqueous solutions were established with the use of a 10 Hz repetitive single spark (RSS) Most of these elements were only detectable at levels above 1 µg/mL, although the detection limit for Li was 0006 µg/mL The relative standard deviation for replicate sample analysis was 4–8% The detectability of some species was enhanced with the use of a 10 Hz repetitive spark pair (RSP): a pair of sparks separated in time by about 18 µs The detection limits for B/H2O with the RSP and the RSS were 80 and 1200 µg/mL, respectively Species were also detected in organic solvents and in flowing samples The laser spark method of liquid analysis would be useful in situations requiring noninvasive monitoring of species at high or moderate concentrations

New lines in the UV: SRS of excimer laser wavelengths

The UV excimer lasers ArF, KrCl, KrF, and XeCl were utilized to create new families of UV lines by multiple orders of broad-band nonresonant stimulated Raman scattering (SRS) in the media H 2 , D 2 , CH 4 , and LN 2 . Mixed-media and excited-state SRS were also studied.

Efficient Raman shifting of ArF and KrF laser wavelengths

A series of uv lines has been generated in the region 190–360 nm by multiple Raman scatterings of the ArF and KrF laser wavelengths. ArF has been shifted in H2 and KrF shifted in H2, D2, and CH4. For the optimized case of KrF pumping H2, better than 50% energy conversion was observed to the first Stokes at 2769 A.

Experimental studies of a KrF and ArF discharge laser

We have explored the operating characteristics of UV preionized discharge lasers producing 10-100 mJ from noble-gas/ monofluoride excimers. We have studied in detail the temporal characteristics of the discharge, the effects of instabilities, variations of circuit parameters, and the effects of varying degrees of preionization on energy deposition and lasing. Spectral characteristics, tuning, stable and unstable resonator geometries, and beam focusability are also discussed. A companion paper presents the results of a computer modeling of the laser.

Dynamic Polymorphism of Some Binary Iron Alloys

Investigations of the pressure‐induced polymorphism of the Fe‐V, Fe‐Mo, Fe‐Co, and Fe‐C alloy systems have been carried out by dynamic techniques. The addition of vanadium to iron is found to raise the transition pressure very strongly, to some 575 kbar for 25 wt% vanadium content. The Fe‐Co study indicates that long‐range order does not have an appreciable effect on the transformation. The initial mixed phase state of the Fe‐Mo system is clearly manifested in the transition behavior, generally fulfilling expectations. Variations of the transition parameters by various sample heat treatments are demonstrated in the Fe‐C system investigation. The dynamic transformation parameters for pure iron have been reappraised, and are found to be Pb=129±1 kbar, v/v0=0.9360±0.0005. A summary of transition pressures for binary iron alloys is provided.

Phase locking two beams by means of seeded Brillouin scattering

We have demonstrated that the phases of the stimulated Brillouin scattering reflections of two separately focused pump beams can be locked to a common phase by a backward seed of pump laser light.

Improved beam quality in double discharge excimer lasers

The cavity configurations of a Tachisto TacII CO/sub 2/ laser, modified for KrF and ArF operation, were varied in order to produce the best beam quality. (AIP)

Detection of beryllium by laser-induced-breakdown spectroscopy

Abstract Using the new technique of laser-induced-breakdown spectroscopy (LIBS) a limit of detection was measured for beryllium in air of 0.5 ng g ( w w ), which is one-third of the OSHA limit for the 8-h average exposure to beryllium. Approximately linear working curves were obtained over the concentration range 0.5 to 2 × 104 ng g−1. The potential application of this technique to a beryllium monitoring instrument is discussed.

ArF laser enrichment of oxygen isotopes

Absorption by air in the optical cavity of an ArF discharge laser removes the 16O2 Schumann‐Runge lines from the broad lasing output centered at 193 nm. Subsequent irradiation of an oxygen cell induces photochemistry of 17O and 18O, resulting in isotopically enriched ozone.

The atomic fluorine laser: Spectral pressure dependence☆

Abstract Atomic fluorine has been lased at pressures up to 30 psia in a double discharge laser with vigorous flashboard pre-ionization. The spectral output of the laser is a function of pressure, with low pressure favoring doublet transitions and high pressure inducing new laser transitions in the quartet manifold.